In well operations, with the insertion and retrieval of tubular materials from a well, it is not uncommon to have a tool located at the lower end of a tubing string become stuck in the well. Rather than leave the entire tubing string in the wellbore, it is occasionally desirable to break the connection between the tool and the remaining portions of the tubing string so that with retrieval of the tubing string, only a small portion of the well is blocked by the stuck tool.
Many tool release mechanisms are used for this purpose. The most common joints between tubing and the well tool involve a threaded interconnection or a common J-latch arrangement. The release of these joints, however, necessitates the rotation of the tubing string in order to effect release of the coupling. In coiled tubing operations, it is virtually impossible to effect rotational movement of the tubing string. With other tubing string systems, it is occasionally also undesirable to employ rotational movement of the string even though such rotation may be possible.
Coupling means which do not require rotation of the tubing string such as compression or bellville springs do not provide sufficient holding force for maintaining the coupling interconnection at all times when it is desired. Release of such couplings resulting from minor impacts can lead to expensive fishing/retrieval operations which might not otherwise be required. Such couplings also require a large amount of annular space for the release mechanism. Thus, with restricted overall diameter of the tool or coupling, very little flow passage remains within the coupling for any given release pressure. In order to accommodate higher release pressures, correspondingly larger annular space must be taken up by the release mechanism. An additional problem with the release of such couplings is the consistency of the release pressure required since overcoming seal and tubing frictional pressure constitutes a large part of the force required to effect release.